1. Field of the Invention
The present invention relates to a tone-generation timing synchronization method for an online real-time session conducted between electronic music devices via a communication network in a synchronized manner. The present invention also relates to an electronic music device with an interface connectible to a communication network and an ability of conducting an online real-time session with its partner device in synchronism with predetermined tone-generation timings.
The present application claims priority on Japanese Patent Application No. 2010-293529 filed Dec. 28, 2010, the content of which is incorporated herein by reference.
2. Description of the Related Art
Electronic music devices with an ability of conducting online real-time sessions with partner devices have been conventionally known and commercially available worldwide. Non-Patent Document 1 discloses a typical electronic music device with is able to conduct an online real-time session with its partner device. This electronic music device, namely “TENORI-ON”, includes performance operators having LEDs that are manually operated to input music information, so that users are able to visually recognize performance operators operated by themselves. Additionally, this electronic music device is able to conduct music performance with its counterpart electronic music device connected thereto via a MIDI cable (where MIDI stands for “Musical Instrument Digital Interface”). In Particular, Non-Patent Document 1 (see pages 7-8) refers to synchronized performance conducted between TENORI-ON instruments according to the MIDI standard in a master-slave manner. Among two electronic music devices connected together via a MIDI cable, one electronic music device serving as a master sends a start command and a MIDI clock signal to the other electronic music device serving as a slave, thus implementing perfectly synchronized performances therebetween.
Apple Computer Incorporated has launched “Game Center” (see Non-Patent Document 2) which is social gaming software providing multiplayer games with an auto-match function for finding game partners around the world. This allows game players to simultaneously perform online games in a synchronized manner but does not necessarily provide online real-time session functionality.
The foregoing electronic music device needs to be directly connected to its counterpart electronic music device via a MIDI cable; hence, it is impossible to conduct synchronized music performance between electronic music devices, located in remote places, which cannot be directly connected via a MIDI cable.
Another system is developed to achieve synchronized performance among a plurality of electronic music devices via a communication network such as the Internet, whereas these electronic music devices need to be synchronized with each other in terms of performance start timings.
Patent Document 1 discloses a performance timing synchronization method in which a master device sends a “ping” command, representing a delay time confirmation signal, to a slave device, and then the slave device sends back its response to the master device, thus calculating a half of a reciprocating time of communication as a communication delay time t1. Herein, a reference time as the performance start timing is set to five seconds counted from the present time, for example, so that the master device sends a performance start signal to the slave device at (5−t1×2) seconds after the present time.
In this method, however, a communication delay time may frequently vary between the time of sending a performance start signal and the time of sending or receiving a “ping” command (which is used for calculating the communication delay time t1). This cause a time deviation between the actual performance start timing and the predetermined performance start timing.